1. Field
The present disclosure is directed to a method and apparatus for multimode terminals. More particularly, the present disclosure is directed to operation of a multimode terminal on different network technologies.
2. Description of Related Art
Presently, the wireless world is experiencing changes in terms of network deployments. In the past, certain areas of the world deployed global system for mobile communication (GSM) networks and other areas employed code division multiple access technology. Currently, with the increasing popularity of code division multiple access (CDMA) technology, these networks are being deployed in GSM-centric geographies, such as China. Also, GSM technology is being deployed in areas, such as the United States, where CDMA is currently in use.
When multiple technological networks co-exist in the same geographical region, multimode terminals can operate on the co-existing networks. To that end, seamless roaming is desired between the networks. Such seamless roaming is currently handled through the operator agreements. The introduction of the removable user interface module (R-UIM) in CDMA, in light of multimode terminals, brings in challenges for seamless mobility if the CDMA R-UIM and the GSM subscriber identity module (SIM) belong to non-cooperative networks.
For example, a multimode terminal can have subscriptions to both GSM and CDMA networks. However the two networks may not be co-operative networks and the information of a subscription on one network may not be known to the other network. In this scenario, it would be useful to optimize the mobile's scanning process based on a received neighbor list because otherwise a serving network could try to authenticate the mobile on a wrong network. This authentication attempt would thus fail and it would be necessary to abort the handoff process.
Thus, mobile initiated handoff across the technological boundaries between different technological networks is a complex issue if the network to be handed off to belongs to a non-cooperative network. Furthermore, problems exist because mobile initiated handoff across technological boundaries unduly increases the time required for handoff.